Great product. Works perfectly to seal envelopes and also for many other uses. I like the disappearing purple color as it helps me to see exactly where I put the glue.
I bought two packs of Staples Permanent Glue Stick and glued some photos onto card stock paper with the product . By next morning all of them had come unglued. As I wanted to use a glue stick I tried another version: Elmer's School Glue which worked fine. I plan to return the unopened second pack of Staples Permanent glue sticks.